Low dust wall repair compound

ABSTRACT

A wall repair compound useful for filling and repairing cracks, holes, and other imperfections in a wall surface includes a conventional filler material, a conventional binder material, and a dust reducing additive which reduces the quantity of airborne dust particles generated when sanding the hardened joint compound. Airborne dust reducing additives include oils, surfactants, solvents, waxes, and other petroleum derivatives. The additive can be added to conventional ready-mixed joint compounds and to setting type joint compounds. A method of reducing the quantity of airborne dust generated when sanding a fully hardened joint compound includes mixing a sufficient quantity of the dust reducing additive with the joint compound prior to when the joint compound has been applied to the wall.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/781,386, filed Feb. 12, 2001, now pending, which is a divisional ofU.S. application Ser. No. 09/208,782, filed Dec. 10, 1998, issued asU.S. Pat. No. 6,358,309.

FIELD OF THE INVENTION

The present invention relates generally to wall repair compounds such asjoint compounds, spackling compounds, and the like used to repairimperfections in walls or fill joints between adjacent wallboard panels.More particularly, the present invention relates to such a wall repaircompound that includes an additive which reduces the quantity ofairborne dust generated when the hardened compound is sanded.

BACKGROUND OF THE INVENTION

Interior walls of residential and commercial buildings are oftenconstructed using gypsum wallboard panels, often refereed to simply as“wallboard” or “drywall.” The wallboard panels are attached to studsusing nails or other fasteners, and the joints between adjacentwallboard panels are filled using a specially formulated adhesivecomposition called joint compound to conceal the joints. The procedurefor concealing the joint between adjacent wallboards, and therebyproducing a smooth seamless wall surface, typically includes applyingsoft wet joint compound within the joint or seam formed by the abuttingedges of adjacent wallboard panels using a trowel or the like. Afiberglass, cloth, or paper reinforcing tape material is then embeddedwithin the wet joint compound, and the compound is allowed to harden.After the joint compound has hardened, a second layer of joint compoundis applied over the joint and tape to completely fill the joint andprovide a smooth surface. This layer is also allowed to harden. Uponhardening, the joint compound is sanded smooth to eliminate surfaceirregularities. Paint or a wall covering, such as wall paper, can thenbe applied over the joint compound so that the joint and the drywallcompound are imperceptible under the paint or wall covering. The samejoint compound can also be used to conceal defects caused by the nailsor screws used to affix the wallboard panels to the studs, or to repairother imperfections in the wallboard panels, so as to impart acontinuously smooth appearance to the wall surface.

Various drywall joint compounds are known for concealing joints betweenadjacent wallboard panels. Conventional joint compounds typicallyinclude a filler material and a binder. Conventional fillers are calciumcarbonate and calcium sulfate dihydrate (gypsum), which are used in“ready mixed” joint compounds, and calcium sulfate hemihydrate(CaSO₄-—½H₂O; also referred to as plaster of Paris or calcined gypsum),which is used in “setting type” joint compounds. Ready mixed jointcompounds, which are also referred to as pre-mixed or drying type jointcompounds, are pre-mixed with water during manufacturing and requirelittle or no addition of water at the job site. Such joint compoundsharden when the water evaporates and the compound dries. Setting typejoint compounds, on the other hand, harden upon being mixed with water,thereby causing dihydrate crystals to form and interlock. Setting typejoint compounds are therefore typically supplied to the job site in theform of a dry powder to which the user then adds a sufficient amount ofwater to give the compound a suitable consistency.

The Koltisko, Jr. et al. U.S. Pat. No. 4,972,013 provides an example ofa ready-mixed (wet) joint compound including a filler, binder,thickener, non-leveling agent, and water. The McInnis U.S. Pat. No.5,277,712 provides an example of a setting (dry mix-type) joint compoundincluding a fine plaster material, such as stucco, a material whichimparts internal strength and workability to the joint compound, such asmethyl cellulose, and a material for retaining water, such as perlite.Additional examples of joint compounds are provided in the Brown U.S.Pat. No. 4,294,622; the Mudd U.S. Pat. No. 4,370,167; the Williams U.S.Pat. No. 4,454,267; the Struss et al. U.S. Pat. No. 4,686,253; theAttard et al. U.S. Pat. No. 5,336,318; and the Patel U.S. Pat. No.5,779,786.

A spackling compound is disclosed in the Deer et al. U.S. Pat. No.4,391,647. While joint compound and spackling compound do many of thesame things and are both smeared onto walls to hide flaws, spacklingcompound is generally lighter, dries more quickly, sands more easily,and is more expensive than joint compound. For simplicity, jointcompound, drywall joint compound, and like expressions are usedthroughout this specification to refer to wall repair compoundsgenerally, including joint compound and spackling compound.

Sanding hardened joint compound can be accomplished using conventionaltechniques including power sanders, abrasive screens, or manual sanderswhich consist simply of a supporting block and a piece of abrasive papermounted on the block. Sanding the joint compound, however, produces alarge quantity of an extremely fine powder which tends to becomesuspended in air for a long period of time. The airborne particlessettle on everything in the vicinity of the sanding site and usuallyrequire several cleanings before they can all be collected, therebymaking cleanup a time consuming and tedious process. The particles mayalso present a serious health hazard to the worker.

The airborne particles are highly pervasive and can enter the nose,lungs, eyes and even the pores of the skin. Results from a studyconducted by the National Institute for Occupational Safety and Healthfound that dust levels in 9 out of 10 test samples taken at test siteswhere workers were finishing drywall with joint compound were higherthan the limits set by OSHA. The report also said that the dust may notbe safe even when it falls within the recommended limits. In addition,the study found that several dust samples contained silica and kaolin, amaterial found in clay, which have been found to cause permanent lungdamage. The report recommended the use of local exhaust ventilation, wetfinishing techniques, and personal protective equipment to reduce thehazard.

In an effort to reduce the dust generation and cleanup problemsassociated with the sanding of conventional joint compounds, variousattempts have been made to develop specialized dustless drywall sanders.The Matechuk U.S. Pat. No. 4,782,632, for example, discloses a drywallsander including a sanding head designed to minimize the release of dustand further discloses attaching a vacuum cleaner to the sanding head tocollect the dust. The Krumholz U.S. Pat. No. 4,955,748 discloses adustless drywall finisher which uses a wet sponge to prevent theformation of airborne dust.

Dust remains a problem, however, when conventional power sanders or handsanders are used to sand conventional joint compounds. A need thereforeexists for a joint compound that can be sanded using conventionalsanders without producing a large quantity of fine particles capable ofbecoming suspended in air. It would also be desirable to provide anadditive that could be mixed with commercially available joint compoundsto inhibit the formation of airborne particles during the sandingprocedure without otherwise interfering with the properties of the jointcompound.

SUMMARY OF THE INVENTION

The present invention provides a wall repair compound, such as a jointcompound or spackling compound which, when sanded, generates a lowerlever of airborne particles than conventional joint compounds. Morespecifically, the present invention provides a wall repair compoundwhich includes a dust reducing additive. Generally, the wall repair orjoint compound includes a sufficient amount of the dust reducingadditive so that when the joint compound is tested as described in thisspecification, it generates a lower quantity of airborne dust than thejoint compound would produce if it did not contain the dust reducingadditive.

The dust reducing additive can be pre-mixed into the wet joint compoundprior to application or applied as a coating to the hardened jointcompound after application. Generally, the dust reducing additivereduces the quantity of airborne dust particles having a size of lessthan or equal to 10 microns to less than 50% of the quantity that wouldbe generated without the additive. In certain embodiments, the quantityof airborne dust particles is reduced by at least 75% compared to amixture without the additive. Most preferably, the level of airbornedust is reduced by more than 90%. In one embodiment, the quantity ofairborne particles generated by sanding the hardened joint compound ofthe present invention was less than 50 mg/m³ and, in certain otherembodiments, less than about 15 mg/m³. The quantity of airborneparticles generated by sanding the hardened joint compound is preferablyless than 5 mg/m³.

It is desirable that the dust reducing additive serve to suppress theformation of airborne particles without significantly interfering withthe desired characteristics of the joint compound. Suitable dustreducing additives include oils, such as mineral oils, vegetable oilsand animal oils, surfactants, oleoresinous mixtures, pitch, solvents,paraffins, waxes, including natural and synthetic wax, glycols, andother petroleum derivatives. Other materials which do not fit within theabove categories may also effectively reduce the quantity of dustgenerated by a joint compound.

The joint compound formulations include a conventional filler materialand a binder material, such as a resin. The joint compound can alsoinclude a surfactant, which may or may not serve to suppress airbornedust formation, and a thickening agent. Prior to hardening, the jointcompound preferably includes a sufficient amount of water to form amud-like spreadable material which can be applied to the wall surface.The present invention further provides an additive which can be admixedwith conventional joint compounds to reduce the quantity of dustgenerated during sanding. The dust reducing additive can be used withboth drying type (i.e. ready mixed) or setting type joint compounds.

The present invention also provides a method of reducing the quantity ofairborne dust generated by sanding a fully hardened joint compound whichincludes mixing a sufficient quantity of a dust reducing additive withthe joint compound prior to applying the joint compound to a wallsurface.

It is also desirable that the present invention provide a joint compoundhaving good plasticity, water retention, cohesiveness, viscositystability, resistance to cracking, sandability, minimal shrinkage, goodpaint adherence, light weight, low cost, good hardening properties, andother properties comparable to those offered by conventional jointcompounds.

These and other features and advantages of the invention will beapparent to those skilled in the art when considered in view of thefollowing detailed description.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of the testing enclosure used to measurethe quantity of airborne dust generated by sanding the wall repaircompounds of the present invention.

DETAILED DESCRIPTION

According to the present invention, there are provided compositionssuitable for filling and repairing cracks, holes, or other imperfectionsin a wall surface, such as the joints between adjacent wallboard panels.The compositions of the present invention include a dust reducingadditive combined with conventional wall repair compound materialsincluding a filler and a binder to form a low dust wall repair compound.Dust reducing additive refers to any ingredient capable of preventing,minimizing, suppressing, reducing, or inhibiting the formation ofparticles capable of becoming airborne. The expressions “airborneparticles” or “airborne dust particles” refer to fine particlesgenerated during the sanding or abrading of the compound which arecapable of being carried by or through the air. Wall repair compoundrefers generally to compositions useful for filling and repairingcracks, holes, and other imperfections in surfaces such as drywall,wood, plaster, and masonry. Wall repair compounds include interiorfinishing and patch compounds such as joint compound, spacklingcompound, wood fillers, plasters, stucco, and the like. The jointcompound can also include a thickener, and other materials found inconventional joint compounds.

Any conventional filler material can be used in the present invention.Suitable fillers include calcium carbonate (CaCO₃) and calcium sulfatedihydrate (CaSO₄-—2H₂O commonly referred to as gypsum) for ready mixedtype joint compounds, and calcium sulfate hemihydrate (CaSO₄-—½H₂O) forsetting type joint compounds. The joint compound can also include one ormore secondary fillers such as glass micro bubbles, mica, perlite, talc,limestone, pyrophyllite, silica, and diatomaceous earth. The fillergenerally comprises from about 25% to about 95% of the weight of thejoint compound based on the total wet weight of the formulation (i.e.including water). More preferably, the filler comprises from about 55%to about 75% of the total wet weight, and most preferably, from about60% to about 70%.

Another ingredient usually present in joint compounds is a binder orresin. Suitable binders include polyvinyl acetate, polyvinyl alcohol,ethylene vinyl acetate co-polymer, vinylacrylic co-polymer,styrenebutadiene, polyacrylamide, other acrylic polymers, other latexemulsions, natural and synthetic starch, and casein. These binders canbe used alone or in combination with one another. The amount of bindercan range from about 1% to about 45% of the joint compound total wetweight. More preferably, the binder comprises from about 1% to about 20%of the total wet weight, and most preferably, from about 4% to about14%. Preferred binders are Rhoplex HG 74M and Rhoplex AC 417M acryliccopolymers available from Rohm and Haas, Philadelphia, Pa.

A surfactant can also be included in the joint compound formulation,particularly when the dust reducing additive includes an oil. Certainsurfactants have also been found to act as dust reducing additives bythemselves. A preferred surfactant is Triton X-405, a nonionicsurfactant available from Union Carbide Chemicals and Plastics Co. Inc.,Danbury, Conn. The surfactant generally comprises less than about 3.5%of the joint compound total wet weight, and preferably less than about0.25%.

Many joint compound formulations also contain a cellulosic thickener,usually a cellulosic ether. Suitable thickeners include methylcellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose,hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxyethylhydroxypropyl cellulose, ethylhydroxyethyl cellulose, and sodiumcarboxymethyl cellulose (CMC). These thickeners can be used alone or incombination with one another. The amount of cellulosic thickener canrange from about 0.1% to about 2% by weight of the joint compound. Apreferred thickener is hydroxypropyl methyl cellulose available from DowChemical Company under the trade designation Methocel.

Another ingredient that can be included in the joint compound of theinvention is a non-leveling agent. Suitable non-leveling agents includeclays such as attapulgus clay, bentonite, illite, kaolin and sepiolite,and clays mixed with starches. Thickeners, such as those describedabove, can also function as non-leveling agents.

To provide a lighter weight joint compound, glass bubbles or a speciallytreated expanded perlite can be added as described in U.S. Pat. No.4,454,267. Additional ingredients which can be utilized in the jointcompound are preservatives, fungicides, anti-freeze, wetting agents,defoamers, flocculents, such as polyacrylamide resin, and plasticizers,such as dipropylene glycol dibenzoate.

In accordance with a characterizing feature of the present invention,the joint compound includes an ingredient which serves to minimize thequantity of airborne particles generated during sanding of the hardenedjoint compound. The additive generally comprises less than 20% of thejoint compound total wet weight. More preferably, the dust reducingadditive comprises between about 0.1% and about 10% of the jointcompound by wet weight percent and, most preferably, between about 1.5%and about 6%.

Many ingredients have been found to effectively. reduce the quantity ofairborne particles generated when sanding the joint compound includingoils such as animal, vegetable, and mineral oils (saturated andunsaturated), and oils derived from petroleum, pitch, natural andsynthetic waxes, paraffins, solvents which evaporate slower than water,terpenes, glycols, surfactants, and mixtures thereof. A preferred dustreducing additive is a mixture of mineral oil and an unsaturated oil,such as corn oil, comprising from about 1.5% to about 6% of the jointcompound total wet weight, and a surfactant comprising from about 0.15%to about 0.40% of the joint compound total wet weight. It has also beenfound that increasing the level of resin in the joint compound may serveto reduce the level of airborne dust generated during sanding.

While the manner by which each additive serves to suppress the formationof particles capable of becoming airborne is not fully understood, somegeneral observations have been made. For example, it was observed thatthe joint compounds containing a dust reducing additive seemed toproduce particles which were larger and heavier than the particlesproduced by joint compounds without a dust reducing additive. Thus, thedust reducing additive may cause the dust particles to agglomerate orstick together, thereby forming large heavy particles which tend not tobecome or remain airborne. The invention, however, is not intended to belimited to any particular mechanism.

The relative quantity of the various ingredients can vary substantiallyin accordance with the invention. Table 1 shows the general range ofeach ingredient for either a setting type joint compound or aready-mixed type joint compound in its wet condition:

TABLE 1 Percent by Weight (Wet) Filler 25–95% Binder  1–45% Thickener <2% Water  2–45% Dust Reducing Additive <20%

TEST PROCEDURE

The test procedure for measuring the quantity of airborne particlesgenerated when sanding the hardened joint compound was as follows.First, each test specimen was prepared according to a specificformulation. The specific formulations for the various joint compoundsare described more fully below along with the method used to prepare thespecimens. The test specimens were approximately five inches long, oneand one-half inches wide, and one quarter of an inch thick (5″ by 1½″ by¼″). Before sanding, each test specimen was allowed to completely hardenfor at least twenty four hours at room temperature in an environmentwhere the relative humidity generally ranged from about 25% to about75%.

Referring to FIG. 1, there is shown the test enclosure 2 that was usedto sand the test specimens 4 a, 4 b, 4 c and measure the quantity ofairborne dust particles generated. The enclosure 2 was a rectangular boxsix feet high, four feet wide, and two feet wide (6′×4′×2′). The top 6,bottom 8, side 10, and rear walls 12 of the enclosure 2 were constructedof wood, and the front wall 14 was constructed of transparent Plexiglas.A generally triangular access opening 16 located about one foot abovethe bottom wall 8 was provided in the front wall 14 to allow theindividual conducting the test to insert his or her hand and arm intothe enclosure and sand the specimen. The access opening 16 had a basedimension of about 7½ inches and a height of about 8½ inches. A movablecover member 18 was provided to allow the enclosure 2 to be completelysealed when sanding was completed. To sand the specimens 4 a, 4 b, 4 c,the cover 18 was arranged in its up position as shown by the solid linesin FIG. 1. When sanding was completed, the cover 18 was pivoteddownwardly to completely cover the access opening 16 as shown in phantom18′.

As shown, three specimens 4 a, 4 b, 4 c of joint compound were preparedon a section of wallboard 20 and the section of wallboard 20 was clampedto a mounting block 22 arranged within the enclosure 2. When tested, thespecimens were located about twelve inches above the bottom wall 8 ofthe enclosure. Each specimen was tested individually and after eachtest, the enclosure was cleaned so that the quantity of airborne dustparticles measured less than 0.5 mg/m³. A particle counter 24 formeasuring the quantity of airborne particles was mounted in the rightside wall about forty eight inches above the center of the specimens 4a, 4 b, and 4 c.

The test specimens were sanded using a model B04552 power palm sanderavailable from Makita Corporation of America, Buford, Ga. The sanderincluded a 4½×4 inch pad equipped with a 120 grit mesh sanding screenmounted over a 5×3½×¾ inch open, semi-rigid, non-woven, heavy duty,stripping, backing pad available from Minnesota Mining and ManufacturingCompany, St. Paul Minn. Sanding was performed at a sanding speed ofapproximately 14,000 OPM (orbits per minute) using ordinary sandingpressure. Ordinary sanding pressure is defined as the amount of pressuretypically required to sand a hardened joint compound. Sanding pressure,therefore, is the manual pressure typically applied by an ordinaryperson when sanding a joint compound. It will be recognized that thesanding pressure can vary depending on the hardness of the jointcompound. Sanding was continued until the specimen was completelysanded. That is, the entire thickness of the specimen was sanded so thata generally smooth wall surface was produced. Care was taken to ensurethat sanding was discontinued before the drywall itself was sanded. Theamount of time required to sand each specimen varied depending on thehardness of the joint compound and the sanding pressure.

The quantity of airborne dust particles was measured starting from thetime sanding was initiated until several minutes after sanding wasdiscontinued. In general, the level of airborne dust was measured untilthe level decreased to less than 50% of its peak level. The quantity ofairborne dust was measured using a DUSTTRAK™ aerosol monitor model 8520available from TSI Incorporated, St. Paul, Minn. The particle countermeasures the number of particles having a size of less than or equal to10 microns. In the Examples, the peak or highest level of airborne dustmeasured during the test is presented.

INGREDIENTS

A summary of the various ingredients used to prepare the joint compoundsin each of the Examples is provided below:

Fillers

-   Calcium Carbonate—Marble Dust available from ECC International,    Sylacauga, Ala.-   Calcium Sulfate Dihydrate—available from J.T. Baker Chemical Co.,    Phillipsburg, N.J.-   Mica—Mica AMC available from Kraft Chemical Co., Melrose Park, Ill.    Mica prevents cracks from forming as the joint compound hardens.-   Kaolin—Aldrich Chemical Co., Milwaukee, Wis.-   Glass Bubbles—K1 (177 microns—0.14 g/cm³) glass bubbles available    from Minnesota Mining and Manufacturing Company, St. Paul, Minn.    Glass bubbles improve the sandability of the joint compound and help    to form a lighter weight joint compound.    Binders-   Rhoplex HG 74M, Rhoplex HG 74P, Rhoplex AC 417M, Rhoplex 2620, and    Rhoplex EC-2848—acrylic resins available from Rohm & Haas,    Philadelphia, Pa.-   Airflex RP-226—vinyl acetate-ethylene copolymer available from Air    Products and Chemicals, Inc., Allentown, Pa.    Waxes-   Octowax 321—available from Tiarco Chemical Div., Textile Robber &    Chemical Co., Dalton, Ga.-   Boler 1070—a paraffin wax available from Boler Inc., Wayne Pa.-   Carbowax 540—synthetic wax available from Union Carbide Corp.,    Danbury, Conn.    Oils-   Corn Oil—conventional corn oil. A suitable corn oil is available    from Eastman Kodak Co., Rochester, N.Y.-   Linoleic Acid—an unsaturated oil, available from Eastman Kodak Co.,    Rochester, N.Y.-   Castor Oil—an unsaturated vegetable oil available from Aldrich    Chemical Co., Milwaukee, Wis.-   Tung Oil—an unsaturated vegetable oil available from Woodworkers    Store, Medina, Minn.-   Mineral Oil—Carnation light mineral oil available from Witco    Corporation, Sonneborn Division, New York, N.Y.    Surfactants

Surfactants were generally included in the joint compound formulationswhen the dust reducing additive included an oil to help emulsify the oiland combine it with a water based joint compound. Certain surfactants,however, were found to have a dust reducing effect when used bythemselves.

-   FC 430—a nonionic surfactant available from Minnesota Mining and    Manufacturing Company, Industrial Chemicals, St. Paul, Minn.-   Triton X-405—a nonionic surfactant (octylphenoxy polyethoxy ethanol)    available from Union Carbide Chemicals and Plastics Co. Inc.,    Danbury, Conn.-   Variquat B-200—a cationic surfactant (benzyl trimethyl ammonium    chloride 60%) available from Sherex Chemical Co. Inc., Dublin, Ohio.-   Steol KS 460—an anionic surfactant (alkyl ether sulfate sodium salt    60%) available from Stephon Chemical Co., Northfield, Ill.-   Span 85—a nonionic surfactant (sorbitan trioleate) available from    ICI Americas Inc., Wilmington, Del.-   Tween 80—nonionic surfactant (polysorbate 80) available from ICI    Americas Inc., Wilmington, Del.    Solvents-   Isopar M—an aliphatic hydrocarbon available from Exxon Chemical Co.,    Houston, Tex.-   Norpar 15—a normal paraffin available from Exxon Chemical Co.,    Houston, Tex.-   Heptane—available from Aldrich Chemical Co, Milwaukee, Wis.-   Isopropanol—available from Aldrich Chemical Co, Milwaukee, Wis.-   Propylene carbonate—available from Arco Chemical Co., Newton Square,    Pa., under the trade designation Arconate HP.-   Tripropylene glycol methyl ether available from Dow Chemical Co.,    Midland, Mich.-   Tripropylene glycol-n-butyl ether available from Dow Chemical Co.,    Midland, Mich.-   Ethylene glycol phenyl ether available from Dow Chemical Co.,    Midland, Mich.-   D. Limonene—a terpene available from SCM Glidden Organics,    Jacksonville, Fla.-   Exxsol D-110—an aliphatic hydrocarbon available from Exxon Chemical    Co., Houston, Tex.-   Exxate 1300—C₁₃ alkyl acetate available from Exxon Chemical Co.,    Houston, Tex.-   Glycerol—available from J.T. Baker Chemical Co, Phillipsburg, N.J.    Thickener-   Methocel 311—hydroxypropyl methylcellulose available from Dow    Chemical Co., Midland, Mich.

EXAMPLES

The invention is illustrated by the following examples which presentvarious embodiments of the invention. In general, the joint compoundswere prepared by: (1) mixing the water and thickener, if any, with thebinder; (2) adding the dust reducing additive; and (3) adding thefillers, mixing continuously. If the formulation contained a dustreducing additive in the form of an oil and a surfactant, the surfactantwas typically added before the oil. More specific procedures used toprepare certain joint compound formulations are described more fullybelow.

Table 2 presents the test results for a control joint compoundformulation which did not contain a dust reducing additive, along withthe formulation and test results for Examples 1–3, each of whichcontained a dust reducing additive in the form of a wax. Eachformulation is presented by wet weight percent of each ingredient, thatis, including water.

TABLE 2 WAXES Formulations by Wet Weight Percent Ingredient Control 1 23 Calcium carbonate 64.3 61.24 44.0 63.34 Mica 2.7 Kaolin 1.0 2.1 1.04Glass Bubbles 4.7 6.0 1.73 Rhoplex AC 417 M 10.1 9.8 17.0 Airflex RP-2265.23 Triton X-405 0.13 0.2 0.16 Stearic Acid 0.75 28% Ammonium 0.38Hydroxide Water 19.9 16.9 24.17 24.87 Octowax 321 7.13 Boler 1070 7.5Carbowax 540 3.63 Airborne Dust 72 mg/m³ 28 mg/m³ 3.5 mg/m³ 5 mg/m³Drying Time 1 day 1 day 1 day 1 dayThe control formulation included a binder (Rhoplex AC 417 M), fillers(calcium carbonate, kaolin, and glass bubbles), and water. After beingallowed to dry for one day, the specimen having the control formulationwas sanded and found to produce a peak quantity of airborne dustparticles having a size of less than or equal to 10 microns of 72 mg/m³.In Example 1, the formulation includes approximately 7% by weight wax(Octowax 321) which reduced the quantity of airborne dust to 28 mg/m³.In Example 2, the secondary fillers mica and kaolin have been replacedby glass bubbles, and a paraffin wax (Boler 321) was added. The quantityof dust generated by the resulting formulation was reduced to 3.5 mg/m³.

The formulation of Example 2 was prepared by combining the wax andstearic acid and heating them to 170° F. until a clear liquid wasformed. Approximately half of the water was then heated to 170° F. andadded to the ammonium hydroxide. The wax-stearic acid mixture was thencombined with the water-ammonium hydroxide mixture, and this mixture wascooled to room temperature while mixing continuously. In turn, theRhoplex AC 417M, the Triton X-405, the remaining quantity of water, thecalcium carbonate, and the glass bubbles were added and mixed to producea uniform mixture.

The joint compound formulation in Example 3 contains a vinyl acetatebinder (Airflex RP-226) and a wax (Carbowax 540—polyethylene glycol).This joint compound formulation exhibited a dust level of 5 mg/m³.Carbowax is synthetic wax which is soluble or miscible in water. Whileparaffins and Carbowax are both considered waxes, they are believed torepresent dissimilar waxes.

Table 3A presents the formulations and test results for Examples 4–9,each of which contains one oil and a surfactant which serve to suppressthe formation of airborne dust particles during sanding.

TABLE 3A OILS Formulations by Wet Weight Percent Ingredient 4 5 6 7 8 9Calcium Carbonate 54.94 54.72 54.72 55.15 56.41 56.6 Glass Bubbles 8.910.8 10.8 8.55 8.25 6.32 Rhoplex AC 417M 15.63 15.57 15.57 15.69 25.7726.31 Triton X-405 0.39 0.39 0.39 0.39 0.21 0.21 Water 15.5 15.44 15.4415.56 6.19 6.32 Corn oil 4.64 Linoleic acid 3.08 3.08 Castor oil 4.66Mineral oil 3.17 Tung oil 4.24 Airborne Dust 2.3 mg/m³ 3.5 mg/m³ 45mg/m³ 2.5 mg/m³ 7 mg/m³ 13 mg/m³ Drying Time 1 day 1 day 30 days 2 days1 day 2 daysIn each example, the oil significantly reduced the quantity of airborneparticles produced during sanding. It will be noted that Examples 5 and6 had similar formulations. In Example 5, however, the specimen waspermitted to dry for only 1 day and in Example 6, the specimen waspermitted to dry for 30 days. By increasing the drying time from 1 dayto 30 days, the quantity of airborne dust generated having a size lessthan or equal to 10 microns increased from 3.5 to 45 mg/m³. It hasgenerally been observed that unsaturated oils, such as unsaturatedvegetable oils and linoleic acid, reduce the quantity of airborneparticles generated after a short drying time (e.g. 1 day) withoutsignificantly affecting the adhesive properties of the joint compound.In addition, the joint compound can be sanded quite easily. After anextended drying time (e.g. 30 days), however, it has been observed thatthe joint compound becomes more difficult to sand and the quantity ofairborne dust particles increases.

As shown in Example 8, mineral oil by itself was also found tosignificantly reduce airborne dust levels after a short drying time. Inaddition, mineral oil has been found to reduce airborne dust levels overan extended period of time. Mineral oil, however, was found to adverselyaffect the adhesive properties of the joint compound.

Table 3B presents the formulations and test results for Examples 10–15,each of which includes a dust reducing additive comprising a mixture ofcorn oil and mineral oil, and a surfactant. In each Example, the mineraloil and corn oil were premixed.

TABLE 3B OIL MIXTURES Formulations by Wet Weight Percent Ingredient 1011 12 13 14 15 Calcium Carbonate 68.65 63.69 63.69 58.07 61.05 61.05Glass Bubbles 4.8 4.8 5.0 5.25 5.25 Mica 3.0 Kaolin 2.4 0.99 0.99 3.03.0 Rhoplex AC 417M 11.0 9.9 9.9 Rhoplex HG 74M 15.13 11.0 11.0 TritonX-405 0.15 0.15 0.15 Variquat B-200 0.20 Steol KS-460 0.20 FC 430 0.15Methocel 311 0.14 Water 11.3 15.5 15.5 18.01 17.0 17.0 Corn oil 0.5 0.990.99 0.5 0.5 0.5 Mineral oil 3.0 3.98 3.98 3.0 2.0 2.0 Airborne Dust 5mg/m³ 1.5 mg/m³ 5.5 mg/m³ 2.5 mg/m³ 10 mg/m³ 7 mg/m³ Drying Time 1 day 1day 19 days 4 days 4 days 4 days

The combination of mineral oil and an unsaturated oil, such as linoleicacid or corn oil which contains some linoleic acid, was found to be alow dust additive that did not significantly adversely affect theadhesive properties of the joint compound and also reduced airborne dustlevels over an extended period of time.

Examples 11 and 12 have similar formulations but in Example 12, thedrying time was increased to 19 days. As shown, the quantity of dustgenerated after 19 days increased only slightly. Thus, the dust reducingcapability of the corn oil-mineral oil mixture remained much more stableover time than the formulations including linoleic acid presented inExamples 5 and 6.

Example 13 shows that significant dust reduction is also achieved whenusing a combination additive of corn oil and mineral oil in a jointcompound that contains a thickener (i.e. Methocel 311). Example 13 wasprepared by premixing the Methocel 311 with the water until a clearliquid was formed. The surfactant FC 430 and resin Rhoplex HG 74M werethen added. Next, the mineral oil and corn oil were premixed and addedto the other ingredients, mixing continuously. The calcium carbonate andglass bubbles were then added.

The formulations of the joint compounds in Examples 14 and 15 weresimilar but Example 14 included a cationic surfactant (Variquat B-200)and Example 15 included an anionic surfactant (Steol KS-460). In bothexamples, the mixture of corn oil and mineral oil together with thesurfactant significantly reduced the quantity of airborne dustgenerated.

Tables 4A and 4B present the formulations and test results for Examples16–28. These examples demonstrate the dust reducing effect of varioussolvents.

TABLE 4A SOLVENTS Formulation by Wet Weight Percent Ingredient 16 17 1819 20 21 Calcium Carbonate 61.18 69.69 63.12 60.18 48.90 60.49 GlassBubbles 3.81 2.97 3.62 3.91 7.96 6.03 Kaolin 1.0 Rhoplex AC 417 13.0910.22 12.44 13.43 30.8 Rhoplex HG 74M 12.0 Triton X-405 0.24 0.19 0.220.25 0.15 FC 430 0.12 Water 18.02 14.07 17.12 18.48 7.7 16.86 Propylenecarbonate 3.66 Tripropylene glycol methyl ether 2.86 Tripropyleneglycol-n butyl ether 3.48 Ethylene glycol phenyl ether 3.75 D. limonene4.52 Glycerol 3.47 Airborne Dust 14 mg/m³ 7.5 mg/m³ 3.5 mg/m³ 4.5 mg/m³5 mg/m³ 19.5 mg/m³ Drying Time 2 days 3 days 2 days 2 days 1 day 1 day

TABLE 4B SOLVENTS Formulations by Wet Weight Percent Ingredient 22 23 2425 26 27 28 Calcium carbonate 69.95 69.95 68.31 68.31 70.69 68.65 69.95Mica 3.0 3.0 3.0 3.0 Kaolin 2.4 2.4 2.4 2.4 Glass Bubbles 3.1 3.1 2.86Rhoplex AC 417 M 7.0 7.0 10.6 10.6 9.82 11.0 7.0 Triton X-405 0.15 0.150.19 0.19 0.18 0.15 0.15 Water 14.0 14.0 14.6 14.6 13.5 11.3 14.0Heptane 3.5 Isopropanol 3.5 Isopar M 3.2 3.2 Norpar 15 2.95 Exxsol D-1103.5 Exxate 1300 3.5 Airborne Dust 105 mg/m³ 160 mg/m³ 7.5 mg/m³ 110mg/m³ 27 mg/m³ 15 mg/m³ 12.8 mg/m³ Drying Time 1 day 1 day 1 day 5 days5 days 1 day 1 dayAs shown in Examples 22 and 23, not all solvents are effective atreducing the quantity of airborne dust. In addition, Examples 24 and 25demonstrate that an additive may be effective at reducing the quantityof dust generated for a given period of time, but that the level of dustwill increase over time as the additive evaporates. Such a formulationmay be desirable since the additive, depending on its volatility, canprovide dust reduction for a predetermined period of time but willdissipate from the joint compound, thereby leaving a joint compoundhaving properties similar to joint compounds without any dust reducingadditive.

Table 5 presents the test results for Examples 29–33 which show thelevel of airborne dust generated by formulations containing differentsurfactants.

TABLE 5 SURFACTANTS Formulations by Wet Weight Percent Ingredient 29 3031 32 33 Calcium 63.91 61.05 61.05 62.98 62.57 Carbonate Kaolin 3.0 3.01.03 1.03 Glass Bub- 5.01 5.25 5.25 4.02 4.61 bles Rhoplex HG 11.03 11.011.0 11.35 11.28 74M Water 17.04 17.0 17.0 17.53 17.43 Triton X-405 3.01Variquat B- 2.7 200 Steol KS- 2.7 460 Span 85 3.09 Tween 80 3.08Airborne 65 mg/m³ 63 mg/m³ 42 mg/m³ 10 mg/m³ 8.5 mg/m³ Dust Drying Time1 day 4 days 4 days 5 days 5 days

It will be noted that in Examples 29–33, the percentage of surfactantadded to the joint compound formulations was significantly greater thanthe quantity used to emulsify the oil in Examples 4–15 which ranged from0.15 to 0.39 percent by weight. In Example 29, the nonionic surfactantTriton X-405 was found to only slightly reduce the quantity of airbornedust compared to the control formulation. Similarly, in Example 30, thecationic surfactant Variquat B-200 was found to slightly reduce thequantity of airborne dust. In Example 31, the anionic surfactant SteolKS-460 was found to moderately reduce the quantity of airborne dust. Itwas noted that each of the surfactants in Examples 29–31 was initiallysolid materials which had to be solubilized in water.

In Examples 32 and 33, the surfactants were liquids which did not dryeasily. In Example 32, the nonionic surfactant Span 85, which isinsoluble in water and has an HLB of 1.8, was found to have asignificant dust reducing effect. In Example 33, Tween 80, which issoluble in water and has an HLB of 15, was found to have a significantdust reducing effect. It was therefore observed from Examples 32 and 33that liquid surfactants which do not dry quickly may themselves serve aseffective dust reducing additives.

Table 6A presents the formulations and test results of Examples 34–36which show the effect that different resins had on dust generation.

TABLE 6A DIFFERENT RESINS Formulations by Wet Weight Percent Ingredient34 35 36 Calcium Carbonate 63.45 64.05 62.23 Kaolin 1.0 1.0 2.91 GlassBubbles 5.5 4.9 5.10 Triton X-405 0.45 0.15 0.15 Water 19.6 19.8 16.5Rhoplex AC 417M 10.0 Rhoplex HG 74M 10.1 10.68 Corn oil 0.49 Mineral oil1.94 Airborne Dust 51 mg/m³ 81 mg/m³ 7 mg/m³ Drying Time 1 day 1 day 1dayExamples 34 and 35 show that Rhoplex AC 417M, a softer resin thanRhoplex HG 74M, may slightly reduce the level of airborne dust. InExample 36, when a dust reducing additive in the form of a corn oilmineral oil mixture was added, the level of dust generated was reducedsignificantly

Table 6B presents the formulations and test results for Examples 37–39which contained a high level of resin.

TABLE 6B HIGH RESIN LEVELS Formulations by Wet Weight Percent Ingredient37 38 39 Calcium Carbonate 58.29 61.02 59.61 Kaolin 0.96 1.01 1.02 GlassBubbles 5.6 1.11 3.41 Triton X-405 0.15 0.16 0.15 Rhoplex HG 74M 35.0Rhoplex 2620 36.7 Rhoplex EC-2848 35.81 Airborne Dust 30 mg/m³ 6 mg/m³*6.5 mg/m³* Drying Time 1 day 1 day 1 day *test discontinued prior tocomplete sanding of specimenIn each formulation, the quantity of resin was at least 35% by weight.While each of the resins included approximately 50% by weight water, itwill be noted that no additional water was added to any of the jointcompound formulations. Rhoplex HG 74M is a harder resin than Rhoplex2620 and EC-2848. The quantity of airborne dust generated for theformulations in Examples 37–39 was found to be less than the quantity ofairborne dust generated by the control joint compound formulation inTable 2, but the formulations in Examples 37–39 were found to haveobjectionable sanding properties. During the testing of the specimens ofExamples 38 and 39, only half of the specimen could be sanded due to therubbery nature of the joint compound.

Table 6C presents the formulations and test results for joint compoundscontaining a vinyl acetate binder (Airflex RP-226). The controlformulation contains a small quantity of surfactant which may serve toslightly reduce dust generation but is otherwise free of a dust reducingadditive. Example 40 contains a dust reducing additive in the form of amixture of corn oil and mineral oil which was found to significantlyreduce the quantity of dust generated.

TABLE 6C VINYL ACETATE BINDER Formulations by Wet Weight PercentIngredient Control 40 Calcium Carbonate 63.01 62.87 Kaolin 1.03 1.03Glass Bubbles 2.07 2.45 Triton X-405 0.15 0.15 Water 28.54 24.7 AirflexRP-226 5.2 5.19 Corn Oil 0.52 Mineral Oil 3.09 Airborne Dust 84 mg/m³ 3mg/m³ Drying Time 1 day 1 day

Table 7 presents the results for tests conducted by applying the dustreducing additive as a coating to a fully hardened joint compound. Ineach test, a specimen formed of Light Weight All Purpose Joint Compoundavailable from United States Gypsum Co., Chicago, Ill. was prepared andallowed to harden for 4 days. The hardened joint compound was thensaturated with the dust reducing additive and allowed to dry for anadditional period of time, either 7 hours or 24 hours. The specimenswere then sanded. It was found that when applied as a coating, the dustreducing additive served to significantly reduce the quantity ofairborne dust particles generated by the joint compound.

TABLE 7 DUST REDUCING ADDITIVE APPLIED AS A COATING Exxsol D 110 IsoparM Airborne Dust 4 mg/m³ 7.5 mg/m³ (Dried 7 hours) Airborne Dust 4 mg/m³ 27 mg/m³ (Dried 24 hours)

Table 8 presents the formulations and test results for joint compoundformulations containing a calcium sulfate dihydrate filler material. InExample 41, a significant reduction in airborne dust generation wasachieved by including a dust reducing additive comprising a mixture ofsurfactant, corn oil, and mineral oil in the joint compound.

TABLE 8 CALCIUM SULFATE DIHYDRATE FILLER Formulations by Wet WeightPercent Ingredient Control 41 Calcium Sulfate Dihydrate 70.36 66.6Rhoplex HG 74M 8.64 9.7 Water 21 19.3 Triton X-405 0.2 Corn oil 0.7Mineral oil 3.5 Airborne Dust 225 mg/m³ 20 mg/m³ Drying Time 1 day 1 day

Table 9 presents test results obtained using several commerciallyavailable joint compounds.

TABLE 9 CONVENTIONAL JOINT COMPOUNDS - NO ADDITIVE Airborne DryingConventional Joint Compound Dust Time All Purpose Joint Compound 100mg/m³ 3 days Light weight All Purpose Joint Compound 155 mg/m³ 3 daysGold Bond Pro Form Prof. Lite Joint Compound  90 mg/m³ 4 days Easy Sand90 Setting Joint Compound 280 mg/m³ 3 daysThe first three joint compounds are ready-mixed type joint compoundsmanufactured and marketed by United States Gypsum Co., Chicago, Ill.,and Easy Sand 90 is a setting type joint compound manufactured byNational Gypsum Co., Charlotte, N.C.

Table 10 shows the effect of adding a dust reducing additive to theconventional joint compounds of Table 9.

TABLE 10 CONVENTIONAL JOINT COMPOUND WITH ADDITIVE Formulations by WetWeight Percent Gold Bond Pro Light weight All Formula Easy Sand 90 AllPurpose Joint Purpose Joint Professional Lite Setting Joint IngredientCompound Compound Joint Compound Compound Joint Compound 96.35 96.3596.35 67.74 Corn oil 0.5 0.5 0.5 0.51 Mineral oil 3.0 3.0 3.0 4.1 TritonX-405 0.15 0.15 0.15 0.15 Water 27.5 Airborne Dust 2 mg/m³ 12 mg/m³ 5mg/m³ 13 mg/m³ Drying Time 3 days 1 day 1 day 2 days

In each case, a premixed dust reducing additive including corn oil,mineral oil, and the surfactant Triton X-405 was added to each of theconventional joint compounds just prior to preparing the specimens,thereby serving to significantly reduce the quantity of airborne dustgenerated by sanding the hardened joint compound.

Table 11 presents the results obtained when a conventional spacklingcompound, also referred to as a wall repair compound, was tested.

TABLE 11 SPACKLING COMPOUND Control 42 Spakfast 100 95.35 Corn oil 0.5Mineral oil 4.0 Triton X-405 0.15 Airborne Dust 11 mg/m³ 3 mg/m³

Spakfast is a wall repair compound available from Minnesota Mining andManufacturing Company, St. Paul, Minn. Spakfast contains a high level ofresin and exhibits a relatively low level of airborne dust. The level ofairborne dust generated, however, was found to be significantly reducedwhen a dust reducing additive including corn oil, mineral oil, and asurfactant was added to the Spakfast formulation. Thus, according to thepresent invention, a dust reducing additive can be added to aconventional spackling compound to significantly reduce the quantity ofairborne dust generated by the spackling compound.

While the formulations of each example has been presented in terms ofthe weight percent of each ingredient, it will be recognized that theformulations can also be presented in terms of the volume percent ofeach ingredient. By way of example, Table 12 presents two representativeformulations in terms of both percent by weight and percent by volume.

TABLE 12 FORMULATION IN WEIGHT VOLUME PERCENT Formulation 1 Formulation2 Ingredient % by Wt % by Vol % by Wt % by Vol Calcium Carbonate 62.2325.66 54.73 14.82 Glass Bubbles 5.10 40.55 10.8 59.12 Kaolin 2.91 1.47 10.34 Rhoplex HG 74P 10.68 10.8 15.57 11.69 Triton X-405 0.15 0.15 0.150.11 Water 16.5 18.37 15.25 11.68 Corn oil 0.49 0.60 0.5 0.42 Mineraloil 1.94 2.40 2 1.82

Since glass bubbles have a low density and calcium carbonate has a highdensity, the percentage of glass bubbles increases significantly whilethe percentage of calcium carbonate decreases significantly whenconverting the formulation from one based on weight to one based onvolume.

The patents, patent documents, and patent applications cited herein areincorporated by reference in their entirety as if each were individuallyincorporated by reference. It will be apparent to those of ordinaryskill in the art that various changes and modifications may be madewithout deviating from the inventive concept set forth above. Thus, thescope of the present invention should not be limited to the structuresdescribed in this application, but only by the structures described bythe language of the claims and the equivalents of those structures.

1. A method of reducing the quantity of dust generated by a drywalljoint compound, said method comprising the steps of a) providing adrywall joint compound comprising filler, water, binder, and at leastone of a defoamer, wetting agent, preservative, fungicide, thickener,non-leveling agent, surfactant, and solvent; and b) subsequently addinga sufficient quantity of dust reducing additive to the drywall jointcompound to reduce the quantity of dust generated by sanding thehardened drywall joint compound by at least 50%, wherein if said dustreducing additive comprises a solvent, the solvent evaporates at a rateslower than water.
 2. The method of claim 1, wherein when the drywalljoint compound of step (a) is allowed to harden and is tested asdescribed in this specification, the joint compound generates a quantityof airborne particles having a size of less than 10 microns which is atleast 72 mg/m³.
 3. A method of reducing the quantity of dust generatedby a drywall joint compound comprising filler, water, defoamer, wettingagent, preservative, fungicide, thickener, non-leveling agent,surfactant, solvent and binder, said method comprising the step ofadding a sufficient quantity of dust reducing additive to the drywalljoint compound to reduce the quantity of dust generated by sanding thehardened drywall joint compound, wherein if said dust reducing additivecomprises a solvent, the solvent evaporates at a rate slower than water.said adding occurring subsequent to the filler, water, defoamer, wettingagent, preservative, fungicide, thickener, nonleveling agent,surfactant, solvent and binder being present in the joint compound. 4.The method of claim 3, wherein the quantity of dust generated by sandingthe drywall joint compound prior to adding the dust reducing additive isat least about 72 mg/m³.
 5. The method of claim 4, wherein the quantityof dust generated by sanding the drywall joint compound after adding thedust reducing additive is no greater than about 10 mg/m³.
 6. The methodof claim 3, wherein the quantity of dust generated by sanding thehardened drywall joint compound prior to adding the dust reducingadditive is reduced by at least 50% after adding the dust reducingadditive.
 7. The method of claim 6, wherein the dust reducing additivecomprises oil.
 8. The method of claim 7, wherein the oil comprises fromabout 1.5% to about 6.0% of the joint compound total wet weight.
 9. Themethod of claim 1, wherein said dust reducing additive comprises atleast one of oil, wax, pitch, paraffin, terpene, and glycol.
 10. Themethod of claim 3, wherein said dust reducing additive comprises atleast one of oil, wax, pitch, paraffin, terpene, and glycol.
 11. Amethod of reducing the quantity of dust generated by a drywall jointcompound comprising filler, water, thickener, non-leveling agent, andbinder, said method comprising: adding a dust reducing additive selectedfrom the group consisting of oils, glycols, waxes, paraffins, terpenes,and combinations thereof, to the drywall joint compound in an amountsufficient to reduce the quantity of dust generated by sanding theresulting drywall joint compound, when hardened, relative to thequantity of dust generated by the hardened drywall joint compound in theabsence of said dust reducing additive.
 12. The method of claim 11,wherein said dust reducing additive comprises synthetic wax.
 13. Themethod of claim 1, wherein said dust reducing additive comprisessynthetic wax.
 14. The method of claim 3, wherein said dust reducingadditive comprises synthetic wax.
 15. A method of reducing the quantityof dust generated by a drywall joint compound, said method comprising:opening a container comprising a dry wall joint compound comprisingfiller, water, thickener, non-leveling agent, and binder; and adding adust reducing additive to the joint compound in an amount sufficient toreduce the amount of dust generated by sanding said joint compound,relative to the amount of dust generated by said joint compound prior tothe addition of said dust reducing additive, wherein if said dustreducing additive comprises a solvent, the solvent evaporates at a rateslower than water.
 16. The method of claim 15, wherein said addingcomprises adding from 0.1% by weight to 10% by weight of said dustreducing additive.
 17. The method of claim 15, wherein said addingcomprises adding from 1.5% by weight to 6% by weight of said dustreducing additive.
 18. A method of reducing the quantity of dustgenerated by a drywall joint compound, comprising the steps of a)providing a drywall joint compound comprising filler, water, binder, andat least one of a defoamer, wetting agent, preservative, fungicide,thickener, non-leveling agent, surfactant, and solvent; and b)subsequently adding a sufficient quantity of dust reducing additive tothe drywall joint compound to reduce the quantity of dust generated bysanding the hardened drywall joint compound by at least 50% relative tothe quantity of dust generated by sanding the hardened drywall jointcompound prior to adding the dust reducing additive, said dust reducingadditive comprising oil.
 19. A method of reducing the quantity of dustgenerated by a drywall joint compound comprising filler, water,defoamer, wetting agent, preservative, fungicide, thickener,non-leveling agent, surfactant, solvent and binder, said methodcomprising the step of adding a sufficient quantity of dust reducingadditive to the drywall joint compound to reduce the quantity of dustgenerated by sanding the hardened drywall joint compound, wherein saiddust reducing additive comprises oil, said adding occurring subsequentto the filler, water, defoamer, wetting agent, preservative, fungicide,thickener, nonleveling agent surfactant, solvent and binder beingpresent in the joint compound.
 20. The method of claim 19, wherein theoil comprises from about 1.5% to about 6.0% of the joint compound totalwet weight.